Maroochy Waterwatch CEO Cerran Fawns says the "crystal clear" Maroochy River has been beneficiary of a dry year with relatively light rainfall reducing the amount of sediment washed into the estuaries.
She said weather was one of the most decisive factors in determining water quality and sediment control but there were other factors that had played a part.
Increased planting in the upper and middle catchment was helping to stabilise banks and contain erosion.
Her group planted 11,000 trees during one project earlier this year and stricter regulations on development requiring revegetation were all helping contribute to cleaner waterways.
THREE of the Sunshine Coast's four major waterways are on a major health kick according to the 2016 Healthy Waterways and Catchments report card.
Maroochy River and Mooloolah River have both improved their gradings, each going from a C+ to a B while the Pumicestone Passage improved from a B- to a B+.
Noosa River remained unchanged with an A- grading, cementing itself as the healthiest waterway in south-east Queensland, alongside only Eastern Bay.
The report criteria evolved last year to include a Waterways Benefits Rating.
Noosa River went from a 4.5-star benefit rating in 2015 to a 4-star benefit rating this year, while Mooloolah River went from a 4-star benefit rating last year to 4.5-stars this year.
Maroochy River (4-star) and Pumicestone Passage (4.5-star) remained unchanged in their benefit ratings this year.
Healthy Waterways and Catchments Science Committee chairman Professor Stuart Bunn said the majority of improvements in the south-east region had been in the coastal zones.
Interestingly, a lack of rainfall was one of the factors highlighted in the Coast catchments report as one factor contributing to a reduced pollutant load entering waterways, leading to the improvements seen in Maroochy, Mooloolah and Pumicestone Passage.
The report said sediment pollutant loads created through rural channel erosion and a "rapidly growing urban footprint" continued to impact waterway condition and benefits and that further action was needed in vulnerable rural and urban areas to "maintain vegetation, stabilise channels and banks and minimise run-off from construction sites".
Unitywater executive manager infrastructure planning and capital delivery Simon Taylor said advanced sewage treatment processes had helped contribute to the improvement.
"We are proud that we meet strict environmental standards and that the effluent we discharge back into the environment is of a very high standard that doesn't threaten water quality," he said.
He said the company's Creekside Greening program had also helped boost waterway health.
"To date, we've planted more than 12,000 seedlings. These planting days, in conjunction with the council and local community groups, help create vegetation buffers to trap sediment and filter run-off before it enters the rivers," Mr Taylor said.
Healthy Waterways and Catchments CEO Julie McLellan said the community was pleased with their waterways and was getting great use out of them.
"The economic value generated through local community waterway recreation is high," Ms McLellan said.
"In order to protect the social and economic benefits from the pressures of urban development, it is critical to incorporate stormwater management infrastructure in new developments, and implement erosion and sediment control on construction sites."
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